Not that Nat and Steve only showed chemistry in The Winter Soldier. Their bond went deeper than that and carried from The Avengers to Winter Soldier, Age of Ultron, Captain America: Civil War, Avengers: Infinity War, and Avengers: Endgame. I wish Steve had been given more time to mourn his friend Nat in Endgame, but her sacrifice was too closely followed by Tony Stark/Iron Man’s death. That’s one regret the Endgame writers shared about Black Widow’s storyline, that the movie had to go on instead of spending time grieving Natasha.
Article source: https://www.cinemablend.com/news/2492628/scarlett-johansson-knows-why-she-and-chris-evans-had-such-great-chemistry-mcu-nat-and-steve